This invention relates generally to radar systems and more particularly to feedthrough hulling arrangements used in radar systems.
As is known in the art, in many applications it is required that a radar transmitter operate at relatively high output power levels yet be of a relatively small size. Further, in order to improve transmitter reliability it is advantageous to use solid-state components. One common solution to these requirements is transmit with a continuous wave (CW) waveform, as distinguished form a pulsed waveform. The use of a CW wave form minimizes transmitter size when implemented with solid-state components because the transmitter design margins are limited by average power rather than peak power requirements of pulsed waveform systems. However, CW radar systems are subject to high levels of transmitter power feeding directly into the receiver. Such effect is commonly referred to as "feedthrough". Such feedthrough can saturate the receiver and prevent proper detection of the desired reflected radar energy. That is, the receiver may be required to provide sensitivities that are near the benign thermal, kTNF, noise floor of the system while maintaining simultaneous operation in a non-distorting manner even in the presence of relatively high feedthrough. Therefore, with the CW system, the requirements for full sensitivity and high linearity become difficult to achieve as the feedthrough levels increase.
One technique suggested to reduce feedthrough is to place the transmitter and receiver at different locations. Such suggestion is not satisfactory where site locations for both transmitter and receiver are limited. Also, the antenna directional patterns required to cover an intended area may require the receive antenna to stare directly at the transmit antenna and thereby exacerbate the receiver desensitization through the presence of high feedthrough levels.
More recently, it has been suggested that the receiving antenna station be remotely located from the radar receiver station with the antenna station being coupled to the receiver station through an optical link.